This invention relates to improvements in devices for manufacturing metal skins, and more particularly, but not by way of limitation, to a device for trimming to a desired net shape a metal skin particularly adapted for use in aircraft.
In the general art of metal fabrication it is desirable to quickly and accurately cut metal to desired shapes for further assembly into a particular component or sub-element. In the field of aircraft manufacture this is especially true since the materials are expensive, the labor to manufacture aircraft costly, and the need for extreme accuracy in the manufacture of detail parts and further assembly is especially acute. In the manufacture of aircraft it is especially important that extreme accuracy be maintained throughout the manufacture of the aircraft. For example, in the manufacture and assembly of the outer metal skins of an aircraft it is extremely desirable to maintain as closely fitting joints between the portions of skins as possible. One reason for this is that gaps between skins in addition be being unsightly and undesirable to a purchaser of the aircraft will cause a roughness in the outer surface of the aircraft and thereby give rise to laminar flow separation. When this occurs and in effect the lamina of air closest to the skin of the aircraft tumbles along the surface, the drag and in turn the specific fuel consumption of the aircraft is increased.
In addition, gaps can also cause undesirable leakage, differentials of thermal expansion and other undesired effects. Generally, manufacturing workers attempt to cut one skin to abut against another to a predetermined extend whereby a undue or varying gap is avoided and a desired gap is achieved in order to accommodate thermal expansion of the aircraft during anticipated operating conditions.
Workers generally assemble one metal skin to the frame of the aircraft fuselage with an edge being cut to a predetermined trueness or net shape prior to attaching the skin to the frame such as by riveting. The adjacent metal skin is then partially attached as by riveting to the frame with a portion permitted to overlap the edge of the previously attached skin. The overlapping portion of metal skin is then scribed or a guiding track provided for cutting the overlapping to a shape that can then be accommodated to the previously attached skin. While these methods have been commonly used in the past, they have been time consuming since great care must be used to avoiding cutting an inaccurate edge on the overlapping skin and thereby necessitate a costly repair to the fuselage of the aircraft.
A need has existed, that has not been satisfied until the present invention, for a hand operated device that may be utilized to quickly and accurately cut to a net shape a metal skin that is in the process of being attached to the frame of an aircraft being manufactured.